PROJECT SUMMARY Myofascial pain is the leading cause of musculoskeletal pain, which affects 85% of the population at some point during their lives and costs Americans more than $50 billion each year. Myofascial pain is characterized by the presence of myofascial trigger points (MTrP), which are hard, palpable, discrete nodules located within taut bands of skeletal muscles that are painful upon compression. Current diagnosis for myofascial pain relies on clinical palpation, which has low reliability. The lack of objective and quantitative clinical diagnostic and outcome measures has led to much controversy regarding myofascial pain and MTrPs, and has resulted in an inability to generate an objective diagnosis, isolate a mechanism of action of effective therapies, or accurately assess the benefits of treatment. In this study, we propose a new technology, Continuous Oscillation Shearwave Elastography (COSE), which uses shear waves generated by continuous vibration of the ultrasound transducer for real-time, high frame rate, quantitative, 2D elastography imaging of MTrPs. COSE does not require the transmission of high voltage, long duration ?push? beams, thus can be implemented on portable, compact, low-cost ultrasound scanners. The following specific aims are proposed. Aim 1: Implement and Optimize COSE on the GE Logiq e Compact Scanner. We will implement COSE on the Logiq e laptop scanner with a user friendly interface for on-line display and continuous update of 2D elastograms. A novel pulse-echo sequence will be used to achieve high frame rate of shear wave detection on the Logiq e. Timing of pulse-echo will be carefully designed to automatically remove tissue strains (due to transducer compression) from the shear waves in the detected motion. Phantom experiments and in vivo tests on patients with MTrPs will be used to validate and optimize the COSE prototype. Aim 2: Pilot Clinical Study. We will use the COSE prototype developed in Aim 1 to study 40 patients with dry needling, which is a common treatment for MTrPs and has been shown to reduce trigger point stiffness. COSE measurements will be obtained before and after the first dry needling treatment, and at week 3 after the final dry needling treatment. COSE results will be compared to clinical evaluations of the MTrPs, including palpation diagnosis by experienced clinicians, pain numeric rating scale, pain pressure threshold, Neck Disability Index, and the cervical range of motion. Successful completion of this project will result in a low-cost, safe, portable, high frame rate, 2D ultrasound shear wave elastography system for objective and quantitative evaluation of MTrPs. This tool will be ideal for point-of-care diagnosis of myofascial pain and treatment evaluation, which is also crucial for investigating the mechanism of action to develop effective therapies.